Berdeaux A, Drieu la Rochelle C, Richard V, Giudicelli J F
Département de Pharmacologie, Faculté de Médecine Paris-Sud, Le Kremlin-Bicêtre, France.
Am J Physiol. 1991 Aug;261(2 Pt 2):H265-70. doi: 10.1152/ajpheart.1991.261.2.H265.
This study was carried out to determine the relative role of alpha- and beta-adrenoceptors at the level of large epicardial and small resistance coronary arteries when sympathetic tone is increased by exercise. The responses of left circumflex coronary diameter and blood flow were examined at rest and during treadmill exercise in seven chronically instrumented dogs during control conditions (saline) and after propranolol administration (1 mg/kg) either alone or in combination with phentolamine (1.5 mg/kg). In control conditions, graded treadmill exercise (5, 10, and 12 km/h) resulted in a progressive increase in coronary artery diameter and decrease in coronary vascular resistance. After propranolol, coronary vascular resistance slightly increased at rest and then progressively decreased during exercise. Surprisingly, coronary artery diameter significantly decreased at rest as well as throughout the exercise period. Phentolamine significantly reduced the propranolol-induced effects on coronary arterial diameter but did not restore the exercise-induced dilation of the large coronary arteries observed during control conditions. In addition, phentolamine prevented the propranolol-induced increase in coronary vascular resistance at rest and reinforced the exercise-induced decrease in coronary vascular resistance observed under propranolol. Thus beta-adrenoceptors are essential in the mediation of exercise-induced dilation of large coronary arteries. In contrast, activation of beta-adrenoceptors is only partially responsible for the decrease in coronary vascular resistance during exercise. Finally, constriction of large coronary arteries after propranolol is mainly explained by the unmasking of alpha-adrenergic tone at rest, but other mechanisms are involved during exercise.
本研究旨在确定在运动使交感神经张力增加时，α和β肾上腺素能受体在大的心外膜冠状动脉和小的阻力冠状动脉水平的相对作用。在对照条件下（生理盐水）以及单独给予普萘洛尔（1mg/kg）或联合给予酚妥拉明（1.5mg/kg）后，对7只长期植入仪器的犬在静息和跑步机运动期间左旋冠状动脉直径和血流量的反应进行了检查。在对照条件下，分级跑步机运动（5、10和12km/h）导致冠状动脉直径逐渐增加，冠状动脉血管阻力降低。给予普萘洛尔后，冠状动脉血管阻力在静息时略有增加，然后在运动期间逐渐降低。令人惊讶的是，冠状动脉直径在静息时以及整个运动期间均显著减小。酚妥拉明显著减轻了普萘洛尔对冠状动脉直径的影响，但未恢复对照条件下观察到的运动诱导的大冠状动脉扩张。此外，酚妥拉明阻止了普萘洛尔诱导的静息时冠状动脉血管阻力增加，并增强了在普萘洛尔作用下观察到的运动诱导的冠状动脉血管阻力降低。因此，β肾上腺素能受体在介导运动诱导的大冠状动脉扩张中至关重要。相比之下，β肾上腺素能受体的激活仅部分负责运动期间冠状动脉血管阻力的降低。最后，普萘洛尔后大冠状动脉的收缩主要是由于静息时α肾上腺素能张力的暴露，但运动期间还涉及其他机制。
